negative video image on iTunes

The iTunes video on my girlfriends computer keeps turning the image into a negative when we are trying to watch movies on her computer. The video starts correctly but changes to a negative a few seconds into the file. Keeping the mouse pointer ontop of the control bar will stop it, but then you have the control bar across the bottom of the screen the whole time.
We have tried everything, from reinstalling Itunes to even reformatting and reinstalling windows(yeah its a PC unfortunatly). She has no other video problems except this specific one with iTunes.

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